Yesterday, Carl posted a photograph of Bell Heather. The other heather species out just now, ahead of the blooming of the Common Heather, or Ling, late in the summer, is Cross-leaved Heath. Superficially similar, the key difference is that the stem leaves of the Cross-leaved species are in distinct and separated whorls of four, while the leaves of Bell Heather are much denser and, if you look closely, in threes. Bell Heather is also usually a much darker purple as Carl's photo shows. The two species can be found growing side by side.